InGaN/GaN Structures: Effect of the Quantum Well Number on the Cathodoluminescent Properties

In this work we compare luminescence results obtained on InGaN/GaN multiple quantum well (QW) structures with 10 and 30QWs. The aim is to increase the intensity of faster blue QW emission and decrease the luminescence of the QW defect band, showing a slower luminescence decay time, which is undesired for fast scintillator applications. We demonstrate that increasing the number of InGaN QWs is an efficient method to reach this goal. The luminescence improvement of the sample with higher number of QWs is explained by the influence of the increased size of V-pits with increased QW number. Thinner QWs on the side wall of V-pits serve as barriers which separate carriers from dislocations penetrating through the V-pit centre, supressing thus the non-radiative and radiative recombination on defects. Based on cathodoluminescence (CL) results, the scintillator structure design is discussed. Scintillator structures with higher number of QWs can take advantage of both, improved luminescence efficiency and thicker active region.